Cardiac injury markers and a failed algorithm: can accurate assessment of acute myocardial infarction be cost effective?

Context: Most studies assessing the use of cardiac injury markers, such as cardiac troponin I (cTnI), total creatine kinase (CK Total), and the cardiac isoenzyme of CK (CK-MB), agree that cTnI is the most specific test for diagnosing acute myocardial infarction (AMI). However, throughout the literature, there are ambiguities and contradictions on assay-ordering criteria. Inconsistent ways of viewing biochemical assessment of acute chest pain leads to cardiac injury marker assay-ordering patterns that can be nonspecific, ambiguous, and costly.

Objective: This study set out to design a cost-effective strategy and to outline criteria for ordering cardiac injury marker assays. This is accomplished by comparing Madigan Army Medical Center (MAMC) testing patterns to guidelines described in recently published prospective hospital studies investigating the markers.

Design: This was a retrospective study analyzing the patterns of 34,412 cardiac marker assays performed on 4,861 patients during 1999 and 2000 at MAMC. A total of 5,850 assays were run from 1,223 patients during the first 6 months of 2001.

Results: The MAMC chemistry section spent more than $100,000 during 1999 for the measurement of cardiac injury markers. During 2000, an algorithm was implemented to place controls on ordering; however, the same dollar amount was spent. CK Total, CK-MB, and cTnI testing represent 3.5% of the tests performed in the chemistry section, but they consumed about 20% of the supply budget. This disproportionate expenditure is attributable to numerous, dissimilar, and voluminous ordering patterns.

Conclusions: Proper use of cardiac marker assays can lead to rapid and accurate diagnosis of AMI and subsequently save lives. This study demonstrates that cTnI is the only marker needed for accurate and more cost-effective assessment of AMI.